Semiconductor devices (which should be construed to encompass a light emitting diodes as well) include a resin-encapsulated portion with a semiconductor element (which should be construed to encompass a light emitting element as well) encapsulated by an encapsulation resin therein for the purpose of protecting the semiconductor element. In a light emitting diode, the resin-encapsulated portion has a function of serving as a lens portion in order to align the directions of light emitted from the light-emitting element to the front direction of the light emitting diode to improve its front luminance.
The latest trend has been to widely utilize light emitting diodes for illumination purpose having a higher luminous flux than before (such as ceiling illumination at home, headlights for automobiles and outdoor lamps). In order to provide a light emitting diode with a higher luminous flux, it is inevitably necessary to integrate light emitting elements, resulting in the lens portion having an increased size and a complicated structure.
As the method for producing a light emitting diode, there have been known so-called compression molding method and transfer molding method where a substrate having a light emitting element mounted thereon, is disposed so that the light-emitting element is located at a certain position in a mold cavity, and an encapsulation resin is packed in the cavity to form a lens portion. In these methods, a mold release film is normally disposed on the cavity surface of the mold to prevent the encapsulation resin and the mold from being fixed together (see Patent Document 1).